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A posteriori error estimates for Darcy-Forchheimer's problem
No full textarXiv admin note: text overlap with arXiv:2104.04864International audienceThis work deals with the a posteriori error estimates for the Darcy-Forchheimer problem. We introduce the corresponding variational formulation and discretize it by using the finite-element method. A posteriori error estimate with two types of computable error indicators is showed. The first one is linked to the linearization and the second one to the discretization. Finally, numerical computations are performed to show the effectiveness of the error indicators
Physical limitations induced by a medium based on wheat bran for the production of biopesticides by Bacillus thuringiensis spp kurstaki
No full textInternational audienceBiopesticides, vectors for the development of the bioeconomy, represent a realisticalternative to petroleum-based chemical pesticides and their known harmfulness to humans and theenvironment. Bacillus thuringiensis is a gram-positive, spore-forming bacterium used for theproduction of biocontrol agents in agriculture. This insecticidal activity is mainly due to theproduction of parasporal δ-endotoxins consisting of an assembly of crystalline proteins called Cry.The European project IPM-4-Citrus (MSCA RISE, No. 734921, 2017-2023) aims to optimise thesebioproductions from 3 strains of Bacillus thuringiensis subsp kurstaki (Lip, BLB1 and HD1) in acomplex medium (wheat bran). The biochemical composition and nutritional limitations induced bythe medium were identified. The physical properties of these heterogeneous suspensions arenecessary for the definition of operating conditions favourable to scale-up. In this study, themorpho-granulometry of substrates, the ability to separate solid-liquid suspension and to clarifyfermentation broth, and their rheological behaviour were studied as a function of substrateconcentration and granulometry
A New Control Scheme for a Single Phase Modular Multilevel Converter Connected to the Grid Under Unbalanced Arm Power Conditions
No full textInternational audienceSingle phase modular multilevel converters (MMCs) are usually controlled by using two DC voltage sources in order to avoid unbalanced power conditions between the upper and lower arms. This paper proposes a method for controlling the single phase MMC connected to the grid by using one DC voltage source instead of two. In the proposed topology, the grid is connected in parallel with the lower arm, thus, creating a power mismatch between the upper and lower arms. The proposed control method injects a DC circulating current for the power transfer between the DC and AC sides and a fundamental frequency harmonic that is able to balance the capacitor voltages of the upper and lower arms under unbalanced arm power conditions. This method ensures the stability of the MMC operation and the grid while reducing the number of the employed DC voltage sources. The efficiency of the proposed method is revealed by simulations conducted on a single phase MMC connected to a low voltage grid using MATLAB/SIMULINK
Drivers and Reversibility of Abrupt Ocean State Transitions in the Amundsen Sea, Antarctica
No full textInternational audienceThe West Antarctic Ice Sheet has lost mass over the last few decades and has thus contributed significantly to global sea level rise. Warming of the oceanic sub-surface seems to have caused an increase in melting under floating ice shelves, particularly in the Amundsen Sea (Jenkins et al., 2018). Depending on the bedrock slope direction (Pattyn et al., 2012; Schoof, 2007) and ice-shelf lateral buttressing (Gudmundsson, 2013), a sufficiently strong and persistent increase in basal melting can lead to a marine ice-sheet instability (MISI), resulting in a self-sustained retreat of the glacier's grounding line and to the acceleration of its flow (Favier et al., 2014; Joughin et al., 2014). Instabilities are triggered above a certain level of ocean warming (critical threshold or tipping point), with the possible existence of multiple thresholds. Thus, Rosier et al. (2021) estimated that Pine Island Glacier would undergo a MISI and major mass loss for an oceanic warming of +1.2°C relative to the present. Garbe et al. (2020) estimated that a tipping point of +2°C global warming relative to preindustrial could cause a MISI of the entir
Optimization of Culture Conditions and Wheat Bran Class Selection in the Production of Bacillus thuringiensis-Based Biopesticides
No full textInternational audienceBacillus thuringiensis is the leading microbial-based biopesticide, thanks to its parasporal crystal proteins or δ-endotoxins, which are toxic to insect larvae upon ingestion. Once in the insect larvae midgut, the crystal is solubilized by the alkaline pH and the δ-endotoxins activated by proteolytic cleavage. Thanks to its high efficiency as a biopesticide, several efforts have been made to enhance its growth and δ-endotoxins production, in various types of culture media. In this study, a culture medium based on wheat bran (WB), the by-product of cereal grain milling, was used to grow Bacillus thuringiensis and produce δ-endotoxins. Using the response surface methodology (RSM), the effects of three variables were evaluated: WB particles granulometry, their concentration, and their agitation in a 48-h shake-flask culture at 30 °C. Three response parameters were targeted: δ-endotoxins production, final culture pH, and dry-matter consumption. According to the RSM results, the optimum would be at 3.7 g WB/50 mL, with a granulometry above 680 μm and agitation between 170 and 270 rpm. This study is key to developing natural and cheap culture media that can be used at an industrial level for Bacillus thuringiensis-based biopesticides
Prevalence of Her2-neu status and its clinicopathological association in newly diagnosed gastric cancer patients
No full textInternational audienceBACKGROUND: This study aimed to report the prevalence of HER2-neu in newly diagnosed early or metastatic gastric cancer (GC) patients, to determine the percentage of patients achieving various IHC scores correlating with the ISH results and to establish a database for GC patients in Lebanon. METHODS: This was a national, multicenter, descriptive and cross-sectional study in patients with histologically confirmed early or metastatic GC newly diagnosed. All eligible patients underwent the IHC and ISH tests in a central laboratory. Demographics, medical history and histopathology data were collected. RESULTS: One hundred fifty-seven patients were included (mean age at diagnosis: 63 ± 14.1 years) during a 3.5 year period. The prevalence of HER2-neu over expression was 21% (95% CI: 15.3-27.4) using ICH and ISH. Agreement between IHC and ISH results was significantly substantial (kappa = 0.681; p-value \textless 0.001). Over expressed HER2-neu status was significantly associated with high ECOG performance status only. CONCLUSIONS: The prevalence of HER2-neu over expression in newly diagnosed early or metastatic GC patients seemed to be high in Lebanon. The database generated allows to monitor trends in the epidemiology and management of GC
Inhibition of Aflatoxin B1 Synthesis in Aspergillus flavus by Mate (Ilex paraguariensis), Rosemary (Rosmarinus officinalis) and Green Tea (Camellia sinensis) Extracts: Relation with Extract Antioxidant Capacity and Fungal Oxidative Stress Response Modulation
No full textInternational audiencePlant extracts may represent an ecofriendly alternative to chemical fungicides to limit aflatoxin B1 (AFB1) contamination of foods and feeds. Mate (Ilex paraguariensis), rosemary (Romarinus officinalis) and green tea (Camellia sinensis) are well known for their beneficial properties, which are mainly related to their richness in bioactive phenolic compounds. AFB1 production is inhibited, with varying efficiency, by acetone/water extracts from these three plants. At 0.45 µg dry matter (DM)/mL of culture medium, mate and green tea extracts were able to completely inhibit AFB1 production in Aspergillus flavus, and rosemary extract completely blocked AFB1 biosynthesis at 3.6 µg DM/mL of culture medium. The anti-AFB1 capacity of the extracts correlated strongly with their phenolic content, but, surprisingly, no such correlation was evident with their antioxidative ability, which is consistent with the ineffectiveness of these extracts against fungal catalase activity. Anti-AFB1 activity correlated more strongly with the radical scavenging capacity of the extracts. This is consistent with the modulation of SOD induced by mate and green tea in Aspergillus flavus. Finally, rutin, a phenolic compound present in the three plants tested in this work, was shown to inhibit AFB1 synthesis and may be responsible for the anti-mycotoxin effect reported herein
Valorization of wheat bran (WB) by-product in the production of Btk based biopesticides
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Caractérisation des phthalates dans l'atmosphère urbaine de deux sites Est-Méditerranéens
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Chemical characterization and source apportionment of PM2.5 in two East-Mediterranean sites
No full textInternational audienceThe East Mediterranean region faces elevated concentrations of PM resulting from transported pollution mixed with anthropogenic emissions (traffic, industrial, and residential emissions), and natural emissions (Saharan and African deserts). It is considered as a hotspot of climate change where model projections show elevated temperatures by the end of the century leading to the increase of photochemical air pollution. Therefore, it is crucial to determine the sources of pollution in the region in order to develop efficient air quality strategies. PM2.5 samples were collected on a 24-hour basis every third day for a year in two urban sites under industrial influence in Lebanon: Zouk Mikael region (ZK) and Fiaa region (FA). ZK is characterized by the biggest power plant in the country which runs on heavy fuel oil, a high density of population (4,200 inhabitants/km2) along with high road traffic and the use of diesel generators for electricity generation. FA is surrounded by chemical industries such as the cement plants along with their corresponding quarries. The samples were characterized for their carbonaceous fraction, water-soluble ions, elements, and organic species (alkanes, PAHs, fatty acids, biogenic secondary organic aerosols, etc.). Several species and tracer compounds were gathered in the USEPA-PMF model in order to assess the contribution of the sources to the PM2.5 concentrations. Crustal dust and secondary ammonium sulfate contributed to 43% and 46% of PM2.5 at ZK and FA. These sources mainly originate from long range transport of air masses as evaluated by HYSPLIT cluster analysis of air mass back-trajectories. Vehicular and industrial emissions were two important sources at ZK contributing to 14% and 13% of PM2.5, respectively. While at FA, vehicular and cement plants emissions contribute together to 13%. Furthermore, open burning of waste explained 16% of PM2.5 concentration at FA. Primary and secondary biogenic emissions contributed to 9% of PM2.5 at ZK and 13% at FA. This study is a first in Lebanon and from the few in the region using extensive dataset on PM2.5 chemical composition with organic and inorganic species and quantifying the contribution of different natural and anthropogenic sources